ostream: Make sure writing to files always fully succeeds or fails.

Don't allow partial writes (to NFS).

--HG--
branch : HEAD

diff --git a/src/lib/ostream-file.c b/src/lib/ostream-file.c
index 7ac7fc600b59354bf24b7efc2489f33275bf22c7..11a78a7d181c3eb85f487ef0f0494d4661257a9f 100644 (file)
--- a/src/lib/ostream-file.c
+++ b/src/lib/ostream-file.c
@@ -161,8 +161,9 @@ static int o_stream_lseek(struct file_ostream *fstream)
 static ssize_t o_stream_writev(struct file_ostream *fstream,
                               const struct const_iovec *iov, int iov_size)
 {
-       ssize_t ret;
+       ssize_t ret, ret2;
        size_t size, sent;
+       bool partial;
        int i;
 
        o_stream_socket_cork(fstream);
@@ -176,11 +177,12 @@ static ssize_t o_stream_writev(struct file_ostream *fstream,
                        ret = pwrite(fstream->fd, iov->iov_base, iov->iov_len,
                                     fstream->buffer_offset);
                }
+               partial = ret != (ssize_t)iov->iov_len;
        } else {
                if (o_stream_lseek(fstream) < 0)
                        return -1;
 
-               sent = 0;
+               sent = 0; partial = FALSE;
                while (iov_size > IOV_MAX) {
                        size = 0;
                        for (i = 0; i < IOV_MAX; i++)
@@ -188,8 +190,10 @@ static ssize_t o_stream_writev(struct file_ostream *fstream,
 
                        ret = writev(fstream->fd, (const struct iovec *)iov,
                                     IOV_MAX);
-                       if (ret != (ssize_t)size)
+                       if (ret != (ssize_t)size) {
+                               partial = TRUE;
                                break;
+                       }
 
                        fstream->real_offset += ret;
                        fstream->buffer_offset += ret;
@@ -199,8 +203,13 @@ static ssize_t o_stream_writev(struct file_ostream *fstream,
                }
 
                if (iov_size <= IOV_MAX) {
+                       size = 0;
+                       for (i = 0; i < iov_size; i++)
+                               size += iov[i].iov_len;
+
                        ret = writev(fstream->fd, (const struct iovec *)iov,
                                     iov_size);
+                       partial = ret != (ssize_t)size;
                }
                if (ret > 0) {
                        fstream->real_offset += ret;
@@ -224,8 +233,42 @@ static ssize_t o_stream_writev(struct file_ostream *fstream,
                stream_closed(fstream);
                return -1;
        }
-
        fstream->buffer_offset += ret;
+       if (partial && fstream->file) {
+               /* we failed to write everything to a file. either we ran out
+                  of disk space or we're writing to NFS. try to write the
+                  rest to resolve this. */
+               size = ret;
+               while (iov_size > 0 && size >= iov->iov_len) {
+                       size -= iov->iov_len;
+                       iov++;
+                       iov_size--;
+               }
+               i_assert(iov_size > 0);
+               if (size == 0)
+                       ret2 = o_stream_writev(fstream, iov, iov_size);
+               else {
+                       /* write the first iov separately */
+                       struct const_iovec new_iov;
+
+                       new_iov.iov_base =
+                               CONST_PTR_OFFSET(iov->iov_base, size);
+                       new_iov.iov_len = iov->iov_len - size;
+                       ret2 = o_stream_writev(fstream, &new_iov, 1);
+                       if (ret2 > 0) {
+                               i_assert((size_t)ret2 == new_iov.iov_len);
+                               /* write the rest */
+                               if (iov_size > 1) {
+                                       ret += ret2;
+                                       ret2 = o_stream_writev(fstream, iov + 1,
+                                                              iov_size - 1);
+                               }
+                       }
+               }
+               if (ret2 <= 0)
+                       return ret2;
+               ret += ret2;
+       }
        return ret;
 }